The present invention relates to thermostats. More particularly, it relates to a time controlled setback thermostat.
Traditionally home heating systems have been controlled by thermostats to maintain the temperature in the home at a desired level. More recently, there have been provided time controlled thermostats which are operable to establish a desired temperature in the residence at a predetermined level during certain selected hours and to maintain the residence at a different temperature level during other selected hours. These latter, so called setback thermostats serve two basic purposes, one to establish comfortable temperature level for different conditions, such as cooler at night for sleeping and warmer during the day for active occupancy of the dwelling. The second purpose is that of economy. The provision of means for reducing the temperature of the dwelling during unoccupied hours and/or during sleeping hours provides an economy in the use of fuel and in the cost of heating the dwelling by a significant amount.
Again, traditionally, such setback thermostats comprise a unitary structure having the clock control mechanism and the thermostat all formed as a single unit. In order to obtain the economy of a setback thermostat by one who already has a conventional thermostat in place would require that the conventional thermostat be replaced by a completely new unit featuring the setback thermostat. Not only are the setback thermostats more expensive but they are also expensive to install, usually requiring the services of an expert installer.
In the art, efforts have been made to provide an add-on structure to modify the structure of a conventional thermostat to simulate a setback action of a conventional thermostat. These have included such efforts as providing a time controlled auxiliary heating element which is placed adjacent the standard thermostat to create the impression at the thermostat that the air space in the dwelling is higher than it actually is, thereby forcing a setback action whenever the auxiliary heater is operating. This arrangement is shown in Anderson U.S. Pat. No. 4,035,752.
In other arrangements, a time controlled mechanism is positioned adjacent a conventional thermostat. A mechanical linkage is provided between the time controlled mechanism and the conventional thermostat to effect a changing of the setpoint dial of the thermostat. These have required a modification of the thermostat to accomodate the mechanical linkage, examples of this type of arrangement are shown in U.S. Pat. Nos. to Angott 4,041,325 and to Helms 4,123,739. In both of these devices some modification must be made to the standard thermostat unit itself in order to accomodate the setback attachment. Further, in both of these structures, the adaptation is accomplished by actually changing the setpoint dial in accordance with the setback determined by the time control unit. Such previous efforts at converting a conventional thermostat to a setback thermostat have proved to be either complex, cumbersome, or both.